Evaluation of the integrity and function of the central nervous system in critically ill patients who are comatose or who have some alteration of mental status currently cannot be done in an ongoing fashion. The purpose of this project is to develop and clinically test a computer-based system for acquisition, analysis, and display of scalp recorded neuroelectric signals (electroencephalogram and evoked potentials). This tool will be used to investigate the degree of dysfunction in neurologically impaired patients, to correlate the indices developed with other measures of cerebral function, and to evaluate the effectiveness of various therapeutic interventions.